Process for the purification of oils



United States Patent rm. (:1. Cg 53/04, 31/14 US. Cl. 208251 11 ClaimsABSTRACT OF THE DISCLOSURE Purification of oils by emulsification in anaqueous medium, breaking the emulsion at boiling temperature by additionof a mixture of finely divided hydrophobic silica and calcium formate,extracting the purified oil from the residue and distilling off thesolvents.

BACKGROUND OF THE INVENTION The invention relates to an improved processfor purification of oils of mineral or vegetable origin by removal ofundesired impurities.

Certain crude mineral oils, residual oils and distillation fractions ofcrude oils contain a significant amount of heavy metals, such as, forexample, vanadium, iron, nickel and copper, which can effect damage tocracking catalysts in cracking processes. In addition the vanadium isespecially very harmful in residual mineral oils which are used asheating fuels as it leads to corrosion and pitting on the metal parts ofthe heating apparatus which can be led back to the interchange actionbetween the metal parts and the hot ashes produced by the combustion ofsuch fuels.

These heavy metals are bound in the form of porphyrin complexes so thatthe usual purification methods are not suited for the removal of thesemetals as the complex compounds of alkyl substituted porphyrins withvanadium and other heavy metals are oil soluble compounds which are lessstrongly absorbed on polar surfaces than high molecular aromatichydrocarbons and the non-hydrocarbons in crude oils or mineral oildistillates. The porphyrin metal complexes are to a far-reaching degreethermally stable so that they sublime at higher temperatures withoutdecomposition or also in view of their sufficient volatility distill andappear in the distillate fractions. Therefore their removal by purelythermal treatment is not possible.

It is known that these metal compounds can be removed from mineral oilsby treating the oil with a sufficient amount of an alkali metal,alkaline earth metal, aluminum or other hydrides in finely divided formto effect decomposition of the complex compounds and after completion ofsuch treatment separating the heavy metals from the oil.

It furthermore is known that lubricating oils during use undergochemical change so that their life is limited. During use aging productsare produced by oxidation, polymerization and cracking which present acomplex mixture which only can be removed from the oil with greatdifiiculty. In addition to such aging products, foreign substances fromexternal sources as by abrasion also can contaminate used oils. As aconsequence, additives, such as, metal salts of organic compounds withan acid hydrogen, have been added to improve the lubricating propertiesand to stabilize the oils against chemical attack in order to maintainthe precipitating aging products in suspension so that no depositsoccur.

Used oils, however, still predominantly contain sub stances with goodlubricating properties so that after removal of the foreign contaminantsand the aging products could be reused or serve as starting materialsfor heavy duty oils if such removal could be substantially quantitative.

Fundamentally the following four procedures come into question forprocessing used oils of the above-mentioned crude oils, residual fueloils and distillation fractions which are contaminated with heavy metalcompounds:

( l) Physical-mechanical processes (2) Extraction processes (3)Adsorption processes (4) Chemical processes Filtration and centrifugingprimarily come into consideration for the first procedure. This methodwhich usually does not result in complete regeneration is only mostseldomly successful in the case of used additive oils as the suspendedparticles are so finely divided by the additive colloid that they cannotbe retained even by high efficiency filters. The methods used inpractice usually depend upon combinations of the four proceduresindicated. Neutral, basic and acidic adsorbents are used, sulfuric acidis primarily used as an extracting agent and chemical regeneratingagent. Sulfuric acid regeneration is accompanied by the disadvantage oflarge oil losses and the characteristic odor of the oil regeneratedthereby.

SUMMARY OF THE INVENTION The object of the invention is to provide aprocess for the recovery of valuable purified crude or used oils whichrenders it possible to remove foreign substances or impurities containedin the oils whereby normal viscous, light yellow and oils are obtainedwhich only have the odor of clean oil.

The essence of the invention resides in that the oil to be purified isemulsified with water with the aid of an emulsifying agent and theemulsion then broken at boiling temperature with a mixture of ahydrophobic silica and an alkaline earth metal formate, especiallycalcium formate, and recovering thepurified oil from the oil containingresidue by extraction and. distilling off the extraction agent. Theprocess can advantageously be carried out continuously in a cyclicprocess.

DETAILED DESCRIPTION OF THE INVENTION INCLUDING PREFERRED EMBODIMENT Theemulsifying agent employed in the preparation of the initial emulsionsof the oil to be purified is not critical as all emulsifying agentssuitable for preparating emulsions of oil and water can be used.Depending upon the oil to be purified either an oil soluble or a watersoluble emulsifier may be employed. Preferably, non-ionic emulsifiersare employed as they permit a greater latitude in conditions. Suitableemulsifiers, for example, can be found among the well-known andcommercially available alkyl polyglycol ethers with about 10 to 20ethoxy groups obtained, for instance, by ethoxylation of fatty alcoholswith ethylene oxide, alkyl phenyl or alkyl naphthyl polyglycol ethers,fatty acid polyglycol esters, fatty acid polyglycol amides, fatty acidpolyglycol ethers produced suitably by ethoxylation of fatty acids,fatty acid amides and fatty amines, as well as similar condensationproducts obtained with ethylene oxide.

The hydrophobic silicas employed according to the invention can befinely divided wet precipitated silicas, pyrogenic silicas produced bypyrogenic decomposition of volatile silicon halides or electric arcsilicas which have been hydrophobized in a known manner withorganohalosilanes, such as, dimethyl dichlorosilane.

Wet precipitated hydrophobized silicas can, for instance, have a BETsurface area of about 20 to 200 m. /g., preferably, about 100-150 m./g., such as, :for example, in a hydrophobized precipitated silicacontaining 98.3-99.0% of silica and about 0.9 to 1.1% of carbon derivedfrom chemically bound methyl groups which cause the hydrophobicity, andhaving a primary particle size of 20-300 m a secondary particle size of0.7-9p, a BET surface area of 20:3 m. /g. and a pH of 3.4-4.9 (4% inwaterzacetone) and a hydrophobized wet precipitated silica containing2.801020% of carbon derived from bound methyl groups having a BETsurface area between 110 and 150 mF/g. and a pH of 6-7 (for instance,Degussa hydrophobized silicas TK70, D17 and D500).

Pyrogenic silicas, for instance, have a surface area between about 100to 200 m. /g. and an average primary particle size of about 10 to 50 me,such as, for example, in the hydrophobized pyrogenic silica Aerosil R972(produced as described in Chemische Zeitung, 89, pp. 437- 400) which isa pure pyrogenic silica which has hydrophobic properties by virtue ofchemically bound methyl groups and has a SiO +CH content 99.8%, a carboncontent l.1i0.2% (corresponding to about 0.6 millimol of (CH per squaremeter), a BET surface area of 1201-30 m. /g., an average primaryparticle size of about me and a pH of 3.6-4.0 (4% dispersion in 1:1methanolzwater).

The quantities of the mixture of hydrophobized silica and alkaline earthmetal iformate employed can, for instance, be between 20 and 100 partsby weight per 100 parts by weight of oil and the proportion of alkalineearth earth metal formate being about 2 to 50 parts by weight per 100parts by weight of hydrophobized silica.

If desired, a small quantity of sulfuric acid can be used to acidity theemulsion which is first produced to assist in the removal of any basicimpurities which, for instance, may give rise to pyridine like odors.

The purified oils obtained according to the invention are odorless, havelittle color, leave practically no ash on combustion and are marked bygood stability with respect to color and oxidation. The dissolvedadditives and their decomposition products are completely removed. Theprocess according to the invention is not limited to the treatment ofimpure mineral oils, such as, for example, used crankcase oils, but alsocan be applied to the purifi cation of vegetable oils.

The following example will serve to illustrate the effectiveness of theprocess according to the invention with reference to the treatment of astrongly contaminated almost black colored used crankcase oil with anunpleasant odor which could no longer be regenerated by known methods.

EXAMPLE 12 g. of the used crankcase oil were first emulsified with 200ml. of water and 4 g. of a non-ionic polyglycol ether emulsifying agent(trimethylol propyl oleate ethoxylated with ethylene oxide to provide 6ethoxy groups) and then acidified with a small quantity of sulfuricacid.

The emulsification etfected dissolving out of the water solubleimpurities and the acidification with the small quantity of sulfuricacid served to remove the basic impurities which smelled similar topyridine.

The emulsion was then broken at boiling temperature within a few minutesby addition of 3 g. of a mixture of weight parts of the finely dividedhydrophobized wet precipitated silica described above having a C contentof about 2.80% and 15 weight parts of calcium formate, whereby the oilphase was adsorbed on the silica. The oil containing adsorbate wascollected by filtering and dried and then was extracted in a Soxhletextractor with petroleum ether. After the petroleum ether was distilledoff, 14 g. of a light yellow oil of normal viscosity which only had theodor of clean mineral oil were obtained. A portion of the oil solubleemulsifier was also adsorbed on the silica and caused the 2 g. averagein the weight of the product.

What is claimed is:

1. A method of purifying impure oils which comprises emulsifying the oilto be purified with water and an emulsifying agent adapted to form anemulsion of oil and water and subsequently breaking the emulsion atboiling temperature by addition of an amount of from 20 to weight partsper 100 weight parts of the oil treated of a finely divided hydrophobicsilica admixed with from 2 to 50 weight parts of an alkaline earth metalformate per 100 weight parts of the oil, extracting the purified oilfrom the oil-containing silica and distilling off the extraction agent.

2. The method of claim 1 comprising in addition slightly acidifying theemulsion with a small quantity of sulfuric acid before breaking theemulsion.

3. The method of claim 1 in which said alkaline earth metal formate iscalcium formate.

4. The method of claim 1 wherein the hydrophobic silica is a wetprecipitated silica having a BET surface area of about 20 to 200 m. g.

5. The method of claim 4 wherein the Wet precipitated silica has aprimary particle size of between 20 and 300 mu.

6. The method of claim 1 wherein the hydrophobic silica is a pyrogenicsilica having a surface area between about 100 and 200 m. g.

7. The method of claim 6 wherein the pyrogenic silica has a primaryparticle size of about 10 to 50 ma.

8. The method of claim 6 wherein the pyrogenic silica is obtained bypyrogenic decomposition of volatile silicon halides.

9. The method of claim 1 wherein the hydrophobic silica is an electricarc silica.

10. The method of claim 1 wherein the emulsifying agent is a non-ionicemulsifier.

11. The method of claim 10 wherein the emulsifier is an alkyl polyglycolether with about 10 to 20 ethoxy groups, an akyl phenyl or alkylnaphthyl polyglycol ether, a fatty acid polyglycol ester, a fatty acidpolyglycol amide, a fatty acid polyglycol ether or a condensationproduct of a fatty acid with ethylene oxide.

References Cited UNITED STATES PATENTS 1,591,744 7/1926 Cross 2O8188FOREIGN PATENTS 283,592 1929 Great Britain.

DELBERT E. GANTZ, Primary Examiner J. M. NELSON, Assistant Examiner U.S.Cl. X.R. 208-188

